Water loss rates (WLR) at various combinations of temperature and relative humidity were measured in the lubber grasshopper Romalea guttata. WLR increased at higher humidities when rates were corrected for saturation deficit and with increasing temperature when the saturation deficit was held constant (17 mmHg). The higher rates with rising humidity may reflect an increase in cuticular permeability caused by the grasshopper altering or relaxing barrier mechanisms that operate in dry air.